Comets rush through the solar system at up to 150,000 miles per hour, making it extremely difficult to actually land a space probe on one of them. The solution? NASA is working on something new, awesomely called a "comet harpoon."

It's not just the immense speed of comets that makes landings difficult. The icy rocks are constantly rotating, and their surfaces tend to be too rugged to allow for any sort of probe to land, collect samples, and take off again. The plan NASA is currently working on is to send spacecraft out to the comet, which will fire a harpoon into the comet at multiple locations, allowing it to collect rock samples from all over the comet.

Scientists at NASA's Goddard Space Flight Center are currently in the design phase, and they are using a large metal ballista that can fire a harpoon over a mile at a speed of 100 feet per second, with over a thousand pounds of force. Lead engineer Donald Wegel discusses how they are working to adapt this basic design to the harsh environment of space:

"We're not sure what we'll encounter on the comet –- the surface could be soft and fluffy, mostly made up of dust, or it could be ice mixed with pebbles, or even solid rock. Most likely, there will be areas with different compositions, so we need to design a harpoon that's capable of penetrating a reasonable range of materials. The immediate goal though, is to correlate how much energy is required to penetrate different depths in different materials. What harpoon tip geometries penetrate specific materials best? How does the harpoon mass and cross section affect penetration? The ballista allows us to safely collect this data and use it to size the cannon that will be used on the actual mission."

Collecting samples from a comet could turn up biomolecules, the basic building blocks of life that ancient comets might have brought to the primordial Earth billions of years ago. The harpoon method also allows the probe to bring its samples back to Earth, which allows for a more complex battery of tests to be performed on the samples, and it also means the samples are still around if more sophisticated analysis methods are developed in the future.